As we were setting up our lab, we started to study different aspects of the interactions between P. aeruginosa and S. aureus. Our aim was to test whether we could observe specific interactions between these species under our experimental conditions. Our main objectives were: 1) To test whether P. aeruginosa was able to inhibit the growth of S. aureus via secreted antimicrobial molecules and 2) To establish conditions under which the sensing of S. aureus by P. aeruginosa was observed, and identify parameters that would affect the sensing and response phenotypes. We observed significant growth inhibition of S. aureus by P. aeruginosa spent media, suggesting that secreted molecules underlie this phenomenon. To identify the specific molecules involved, we also initiated construction of P. aeruginosa strains that lacked the biosynthetic machinery for several known growth-inhibitory molecules. Additionally, we observed that P. aeruginosa was able to sense one or more molecules secreted by S. aureus, and increase its antimicrobial activity. Further, we were able to observe this phenomenon even in the absence of known determinants of such an antimicrobial response, suggesting that additional molecules likely play a role in this fascinating interaction. We are currently working towards identifying the genes and pathways that underlie this phenomenon.